The present invention relates to compositions and methods for monitoring and controlling termite infestations and, more particularly, to such compositions and methods which provide bait compositions utilizing purified cellulose and/or micro-crystalline cellulose molded or compacted into desired shapes (e.g. tablets) with optimum density for increased bait loading capacity when placed in termite bait stations.
Termites are well known for their destructive effects on residences, businesses and various other structures. The damage from termite infestations results in huge economic losses, structural safety concerns, and destruction of architecturally valuable structures. Prior to the 1990's, the most widely accepted method to control termite infestation was to create a termite toxic barrier around the structure to be protected by digging trenches or boring holes at regular intervals and pumping in or injecting insecticide. While this method is often effective, physical circumstances, environmental sensitivity or other concerns make this method of control unsuitable at times. The technology of termite baiting was developed to overcome these disadvantages.
One strategy of the current termite baiting technology involves burying bait stations, usually some variation of a hollow tube with perforations and a removable top, around the perimeter of a structure at regular intervals of 8 to 10 feet for example, and adding some type of wood or cellulose to the station for bait or the monitoring matrix. The stations are then monitored for termites on a regular basis, e.g. on a monthly interval. When the wooden or cellulose bait is observed to be infested with termites, it is replaced with bait containing an active ingredient for killing or controlling the termites. Typically, the active containing bait is a paper or wood based product.
Since each bait station has to be placed underground, holes must be dug at regular intervals. Rocky and hardpan soils can make this operation very labor intensive and thus expensive. It is therefore desirable to make the insertion holes as small as possible. A hole size of approximately 2 inches or less in diameter is the most convenient size for current conventional one man power boring equipment. However, this 2 inch diameter hole size limits the amount of currently available wood or active bait that can be contained in the bait station. Currently available termite baits are not of optimum density due to air voids in the wood and paper product bait materials employed in the art. The bait loading capacity of current 2 inch bait stations therefore limits the time for monitoring and refilling the bait stations to approximately one month or less.
Substantial labor saving would be realized if the monitoring intervals could be extended to longer periods of time. Existing bait station designs having diameters of 4+ inches extend the monitoring time to 90 days, but installation requires the use of 4 inch post hole digging equipment. This in turn requires either large heavy equipment or very labor intensive manual post hole diggers. Both methods generate substantial amounts of soil excavated from the holes which requires disposal that adds to labor costs. The decreased labor costs for using such a larger bait station do not compensate for the costs of installation.
Another benefit from extended monitoring times is that since the station is not opened as frequently for monitoring, the termites are disturbed fewer times. It is believed that termites may abandon areas that are disturbed too often.
U.S. Pat. Nos. 5,096,710 and 5,300,293 are directed to bait compositions in tablet form which comprise as essential components (a) at least one insect-growth controlling agent; (b) dextrin with or without (c) a plant oil. Both of these patents specifically mention tableting pressures of about 10 to about 500 kg/cm2.
There remains a need for improved bait compositions and methods which allow maximum bait weight to be loaded into termite bait stations to extend the monitoring time and reduce labor costs.